This Center assists investigators in the U.S.A. and abroad in the identification of arboviruses. The Center maintains a complete collection of virus seeds, antigens, and immune fluids which it uses for its own work as well as distributing them on request to specialized laboratories. During 1974, the Center received virus and/or antiserum to 125 strains from 15 countries. Viruses were identified from Iceland, Ethiopia, Thailand, Portugal, Kenya, India, Trinidad, and several areas of the U.S.A. At least 10 of these are either new viruses or new to the geographic region or host in which they were found. Of particular interest was assistance given by the Center in the investigation of Lassa fever in Nigeria in 1974. New techniques for study of arboviruses were developed including a method for detecting contaminant arboviruses in insect cells and the use of mosquito tissue culture as a field isolation tool. The goal for next year is the identification of 80 viruses from the Americas and other parts of the world. New techniques for study of the antigenic, biologic, and physico chemical properties of viruses of major human disease potential such as Crimean hemorrhagic fever-Congo, yellow fever, dengue, and Venezuelan encephalitis are being developed and will be stressed.